370 A NATURALIST IN THE PACIFIC CHAP. 



Journals the occurrence of P. natans in the Neongong Lake in the 

 Himalayas, and the presence of coots, he most probably mentioned 

 the bird that brought the plants, coots being active distributors of 

 the seeds of water plants. It is of importance to remember that 

 (as shown in my experiment on the duck) seeds of water-plants are 

 voided in a condition peculiarly favourable to early germination. 

 Ducks, coots, and other water birds might often be characterised as 

 " travelling germinators." My experiment showed that seven to 

 eight hours at least were occupied by Potamogeton nutlets in 

 passing through the digestive canal of a duck, and that probably 

 nine or ten hours would be required after an average full meaL 

 But this does not represent the possible maximum period, since the 

 bared " stone " may remain in the gizzard for a long time with 

 ordinary gravel. Most of the Potamogeton fruits found by me in 

 wild ducks were obtained from the gizzard, where they were mixed 

 with gravel and other hard seeds or seedvessels, as described in 

 Chapter XXXIII. Such fruits afterwards germinated. With 

 regard to the chances, therefore, of the fruits of Potamogeton being 

 carried by a bird without injury across an ocean, we may infer that, 

 whether they are retained in its body for only ten hours or for as 

 long as three or four days, they will preserve in some cases their 

 germinating power. 



HAWAIIAN GENERA FOUND IN TAHITI TO THE EXCLUSION 



OF FIJI. 



Taking only the genera that are strictly indigenous, and 

 excluding therefore all those introduced by the aborigines, the 

 number available for establishing an independent connection 

 between the Hawaiian and Tahitian regions is exceedingly few. 

 Amongst the Hawaiian shore-plants not found in Fiji proper but 

 occurring in the Tahitian region are Heliotropium anomalum and 

 Sesuvium portulacastrum. The last-named, however, has been 

 recorded from Tonga, which lies within the Fijian area ; whilst the 

 first will probably be found in the same region. Amongst the 

 Hawaiian and Tahitian mountain genera not recorded from Fiji 

 proper are Nertera, Vaccinium, Cyathodes, and Luzula. As is 

 pointed out in Chapter XXIIL, the absence of these genera from 

 Fiji is connected with the relatively low elevation of those islands, 

 though it is quite possible that one or more of them may yet be 

 found on the highest summits of Fiji ; and indeed Nertera depressa 



